Seismic Upgrades in the Watershed

The San Francisco Public Utilities Commission (SFPUC) is completing the $4.6B Water System Improvement Program (WSIP) which includes seismic upgrades to the Hetch Hetchy water system that crosses three major faults and several minor fault areas. Operating in close proximity to several significant seismic/geotechnical risks, the Hetch Hetchy water system stretches 156 miles from source water high in the Sierra-Nevada Mountain Range, stretching all the way to the City of San Francisco and providing water to 2.4 million people. Along with increasing levels of service concerning delivery, operational, and water supply reliability, the intention of the WSIP is to increase the seismic reliability of SFPUC's Hetch Hetchy water system with the primary level of service goal to maintain or restore - within 24 hours - potable water supply to 24 San Francisco Bay Area municipalities. The Crystal Springs - San Andreas Transmission System Upgrade Project (CSSATSUP), one of 81 WSIP projects, is spread out over 8 miles of environmentally sensitive San Francisco Peninsula Watershed and has 7 different project jobsites which cross, or are within close proximity to, the San Andreas Fault (SAF) as well as some other minor fault zones. The Crystal Springs/San Andreas Transmission System (CSSATS) transmits water between three reservoirs which, in turn, supply source water to Harry Tracy Water Treatment Plant (HTWTP) for use as both supplemental and emergency drinking water. The peninsula watershed reservoirs serve as the only emergency water supply for 1.4 million people on the San Francisco peninsula. The CSSATSUP includes seismic retrofit upgrades to a submerged culvert that crosses the SAF, four reservoir outlet structures less than 1000 feet away from SAF and a 6-mile long, 60" diameter steel pipeline rehab that runs adjacent to SAF, as well as construction of a new electrical substation and new pump station. This paper discusses how a diverse multi-agency project delivery team successfully developed and implanted seismic retrofit upgrades to an aging water transmission system which is subject to significant seismic risk. Also included are details regarding how the CSSATSUP design was developed, an overview of the CSSA system, system operational constraints, technical challenges and the implementation of design during construction of the San Andreas Outlet Structure 2(SAOS2).